Confinement of Organic–Inorganic Hybrid Perovskites within MOF Cavities for Synergistic Regulation of Third-Order Nonlinear Optics

Exploring the regulatory effect of organic-inorganic hybrid perovskites on the third-order nonlinear optical (NLO) properties of MOFs is of great significance. In this work, we used Co-MOF {[Co1.25(HL)0.5(Pz-NH₂)0.25(μ₃-O)0.25(μ₂-OH)0.25(H₂O)]·0.125 Co·0.125 L·10.25 H₂O}(where L = 5,5'-(1H-2,3,5-triazole-1,4-diyl)diisophthalic acid) as the host framework and confined the outstanding optical properties guest molecules AaPbXb {X = Br or I; A = 4BrMBA (a = 2; b = 4) or MBA (a = 1; b = 3)} into the cavities, investigating the regulatory effect of perovskite on the third-order NLO properties of Co-MOF. The third-order NLO tests indicated that Co-MOF displays saturated absorption and self-defocusing refraction behaviors, while AaPbXb@Co-MOF demonstrates excellent antisaturated absorption and self-focusing refraction properties. Furthermore, compared with AaPbXb, the third-order nonlinear optical intensity of AaPbXb@Co-MOF has increased by 3 times. Femtosecond transient absorption spectroscopy (fs-TAS), time-resolved pump-probe spectroscopy, and theoretical calculations were employed to investigate the regulatory mechanism of the NLO properties, revealing that Co-MOF exhibits a ground-state bleaching mechanism, (R-4BrMBA)₂PbBr₄ displays a two-photon absorption mechanism, and (R-4BrMBA)₂PbBr₄@Co-MOF demonstrates two-photon absorption and two-photon-induced excited-state absorption mechanisms. This study provides a reference for perovskite regulation of MOFs' NLO performance.